Google has announced its entire global business will be powered by renewable energy in 2017. The internet giant had first made its pledge to be powered solely by renewables back in 2012. In the five years since then the company has embarked on an aggressive strategy to rid itself of any reliance on energy produced from fossil fuels.

Making the announcement, Urs Hölzle, Google’s Senior Vice President for Technical Infrastructure, said: “This is a huge milestone. We were one of the first corporations to create large-scale, long-term contracts to buy renewable energy directly. Today, we are the world’s largest corporate buyer of renewable power, with commitments reaching 2.6 gigawatts (2,600 megawatts) of wind and solar energy. That’s bigger than many large utilities.”

Google is not alone in its drive to power a global corporation using renewable energy, but it is far and away the biggest buyer of clean energy among the major Western corporates. For Google the drive for clean energy begins at home. Look down on the roof of its headquarters in Mountain View, Silicon Valley and you will see the biggest corporate solar power array in the world. Google says the system produces 1.9 megawatts, enough to supply 30 percent of the power needed to run Mountain View during peak periods.

Powering Mountain View sends a message of commitment from Google HQ, but its energy needs are a drop in the ocean compared with the huge amount of electricity it takes to power the trillions of searches, downloads and uploads happening every minute across Google platforms. In 2015, Google’s activities consumed 5.7 terrawatt hours of electricity across all of its operations. That was almost as much as the city of San Francisco used in the same year.

In order to meet the colossal demand, Google buys energy directly from suppliers; its biggest purchase is from wind farms. Google describes wind energy as ‘essentially free’, as there is no requirement for fuel to generate the electricity.